**7.4.4 Contained lesion**

154 Modern Arthroscopy

**Case 3:** A biopsy specimen was obtained 1 year after surgery from a 52-year-old woman

**Case 4:** A biopsy specimen was obtained 10 months after surgery in a 43-year-old woman with lateral patellar maltracking. There was a grade III/IV defect measuring 2.5 X 3.5 cm over the lateral patella facet. Lateral patella release was performed in addition to

**Case 5:** Biopsy was performed at 18 months after surgery in a 19-year-old man with lateral patellar maltracking and a lateral trochlear grade IV lesion measuring 0.8 cm in diameter.

Chondral core biopsy specimens in cases 2, 3, 4, and 5 with histologic staining with H&E showed columnar morphology of cells with a pale blue ground substance. Safranin-O showed intense orange / red staining of the newly regenerated cartilage zone throughout the regenerated cartilage layer with a propensity toward the deeper areas of cartilage above the subchondral bone. The matrix also showed a predominance of collagen type II deposits, whereas collagen type I was minimal and located mostly over the superficial regions of the articular surface. These compositional results are features of hyaline as opposed to

Fig. 23. Second-look arthroscopy and histological images of a lesion from the lateral femoral condyle (Case 3), a lesion from the lateral patella facet (Case 4) and a lesion from the lateral

with an isolated grade IV lesion of the lateral femoral condyle measuring 2 X 1 cm.

Subchondral drilling was performed followed by lateral patellar release (Fig 23).

fibrocartilage (Kang et al, 2008; Saw et al, 2009 & Lee et al, 2007).

subchondral drilling.

trochlear (Case 5).

In a typical chondral lesion of the medial femoral condyle (Fig 24) measuring 2cm x 2cm, chondrogenesis progresses as described in Fig 24.

Fig. 24. Chondrogenesis: Contained lesion. (A) A blood clot scaffold is formed after subchondral drilling and abrasion chondroplasty between the drill holes. The surrounding articular cartilage is normal with the underlying calcified cartilage layer and subchondral bone. (B) Injection of fresh PBPC plus HA 1 week after surgery results in the homing of the PBPC into the blood clot scaffold. (C) The PBPC residing in the osteochondral junction and blood clot scaffold gradually transform to chondrocytes. HA helps to reduce inflammation and provide raw material for chondrogenesis. The injected PBPC exert paracrine effects and recruit in-situ progenitor cells to assist in chondrogenesis. Repeated injections of PBPC plus HA enable more cells to be recruited into the chondral defect and enhance chondrogenesis. (D) The final result is the formation of a new layer of articular cartilage with good integration to the surrounding tissues. The ossification of the chondrocytes below the articular cartilage results in repair of the subchondral bone with re-establishment of the calcified cartilage layer.

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Fig. 26. Chondrogenesis: Uncontained lesion—ideal drilling. (A) Ideally placed subchondral drilling (1 to 2 mm apart) and abrasion chondroplasty between the drill holes increase the available bony areas for the homing of the PBPC. (B) Injected PBPC and HA have a larger surface area of raw bone providing homing signals for the recruitment of the PBPC. (C) Individual tufts of cartilage arise from the subchondral bone and coalesce to cover the bony defect. (D) Maturation will result in an increase in thickness of the regenerated cartilage

**7.4.7 Further cases to support the theory of chondrogenesis with ideal drilling in** 

technique, adjuvant PBPC & HA therapy and cell viability.

The following cases illustrate the advances made in the light of the histological findings following second-look arthroscopy as regards to the importance of meticulous surgical

Chondral lesions in difficult to access region of the knee joint presented a special challenge to treatment. An example would be the posterior aspects of the medial and lateral tibial plateau. In the early phase of the clinical trial, the first author used a technique called the "Inkwell" (Fig 27) procedure in which a 4 mm burr was used to create multiple half moon-

covering the entire defect.

shaped pits into the bone surface.

Fig. 27. Illustration of an "Inkwell" procedure.

**uncontained lesion** 

### **7.4.5 Uncontained Lesion – Sparse drilling**

Second-look arthroscopy in case 2 revealed tufts of cartilage in between areas devoid of regenerated cartilage. The subchondral drilling over the lateral patellofemoral joint was spaced at 3 to 5 mm apart. Fig 25 provides an explanation. As a result, we have refined our techniques so that a goal of 1 to 2 mm between drill holes is now sought. Abrasion chondroplasty up to a depth of 1 mm is also performed.

Fig. 25. Chondrogenesis: Uncontained lesion—sparse drilling. (A) In large chondral defects with areas of bare bone, the only available blood clot scaffold is from the areas after subchondral drilling. (B) Injection of fresh autologous PBPC plus HA 1 week after surgery will result in the homing of the PBPC into the subchondral blood clot scaffold, with the PBPC residing in the blood clot scaffold. (C) Because there is no blood clot scaffold superficial to the subchondral bone, chondrogenesis can only be achieved by the protruding tufts of cartilage from the subchondral bone drilling. (D) If the subchondral drill holes are placed too far apart, the end result is the incomplete coverage of the subchondral bone with individual tufts of cartilage seen between areas devoid of cartilage.

#### **7.4.6 Uncontained Lesion – Ideal drilling**

Ideally placed drill holes with abrasion chondroplasty allows for a larger surface area and volume of blood clot scaffold to form. When seeded with PBPC and HA, chondrogenesis progresses evenly and the individual tufts of growing cartilage coalesce to form a new layer of articular hyaline cartilage.

Our current method of subchondral drilling in large uncontained lesion is shown in Fig 26.

Second-look arthroscopy in case 2 revealed tufts of cartilage in between areas devoid of regenerated cartilage. The subchondral drilling over the lateral patellofemoral joint was spaced at 3 to 5 mm apart. Fig 25 provides an explanation. As a result, we have refined our techniques so that a goal of 1 to 2 mm between drill holes is now sought. Abrasion

Fig. 25. Chondrogenesis: Uncontained lesion—sparse drilling. (A) In large chondral defects

superficial to the subchondral bone, chondrogenesis can only be achieved by the protruding tufts of cartilage from the subchondral bone drilling. (D) If the subchondral drill holes are placed too far apart, the end result is the incomplete coverage of the subchondral bone with

Ideally placed drill holes with abrasion chondroplasty allows for a larger surface area and volume of blood clot scaffold to form. When seeded with PBPC and HA, chondrogenesis progresses evenly and the individual tufts of growing cartilage coalesce to form a new layer

Our current method of subchondral drilling in large uncontained lesion is shown in Fig 26.

with areas of bare bone, the only available blood clot scaffold is from the areas after subchondral drilling. (B) Injection of fresh autologous PBPC plus HA 1 week after surgery will result in the homing of the PBPC into the subchondral blood clot scaffold, with the PBPC residing in the blood clot scaffold. (C) Because there is no blood clot scaffold

individual tufts of cartilage seen between areas devoid of cartilage.

**7.4.6 Uncontained Lesion – Ideal drilling** 

of articular hyaline cartilage.

**7.4.5 Uncontained Lesion – Sparse drilling** 

chondroplasty up to a depth of 1 mm is also performed.

Fig. 26. Chondrogenesis: Uncontained lesion—ideal drilling. (A) Ideally placed subchondral drilling (1 to 2 mm apart) and abrasion chondroplasty between the drill holes increase the available bony areas for the homing of the PBPC. (B) Injected PBPC and HA have a larger surface area of raw bone providing homing signals for the recruitment of the PBPC. (C) Individual tufts of cartilage arise from the subchondral bone and coalesce to cover the bony defect. (D) Maturation will result in an increase in thickness of the regenerated cartilage covering the entire defect.

#### **7.4.7 Further cases to support the theory of chondrogenesis with ideal drilling in uncontained lesion**

The following cases illustrate the advances made in the light of the histological findings following second-look arthroscopy as regards to the importance of meticulous surgical technique, adjuvant PBPC & HA therapy and cell viability.

Chondral lesions in difficult to access region of the knee joint presented a special challenge to treatment. An example would be the posterior aspects of the medial and lateral tibial plateau. In the early phase of the clinical trial, the first author used a technique called the "Inkwell" (Fig 27) procedure in which a 4 mm burr was used to create multiple half moonshaped pits into the bone surface.

Fig. 27. Illustration of an "Inkwell" procedure.

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Fig 30. A 53-year-old male underwent high tibial osteotomy: (A) Preoperative XR showing narrowing of medial compartment; and (B) Postoperative view at 7 months showing re-

Fig. 31. Preoperative (Pre-op) MRI (STIR) showing 'bone on bone' over the medial compartment of the right knee (red arrow). White arrow showing regenerated articular cartilage at 18 months over the anterior half of both the medial femoral condyle and medial

appearance of the medial compartment.

tibial plateau.

**Case 6**: A 53-year-old man with a varus knee presented with the loss of the articular cartilage over the medial compartment. He underwent a high tibial osteotomy with the fixation of a Tomofix plate. Postoperative intraarticular injections of PBPC in combination with HA were given in accordance with the standard protocol.

The medial femoral condyle underwent ideal subchondral drilling of the uncontained lesion (Fig 28). In the medial tibial plateau, ideal subchondral drilling was performed over the anterior half of the tibial plateau. Due to poor access, it was not possible to perform subchondral drilling over the posterior half of the tibial plateau. Therefore the "Inkwell" procedure was applied over the posterior half of the tibial plateau (Fig 29).

Fig. 28. The corresponding arthroscopic views over the medial femoral condyle. (A) Intraoperative view and (B) view at 18 months.

Fig. 29. (A) Arthroscopic view with black arrow showing ideal subchondral drilling over the anterior half of the medial tibial plateau. Red arrow showing the multiple "inkwells" created in the posterior half of the medial tibial plateau. The blue line indicates the border separating the two distinct procedures. (B) Second-look arthroscopy at 18 months showing ideal chondrogenesis in the anterior half of the tibial plateau as compared to the posterior half.

Fig 30 shows the radiological reappearance of the medial articulation at 7 months after surgery. MRI scan at 18 months confirmed the presence of repair cartilage over the anterior half of the medial compartment (Fig 31), confirmed on second-look arthroscopy (Fig 29). This is in contrast with the repair appearance of the posterior half of the tibial plateau (Figs 29 and 32).

**Case 6**: A 53-year-old man with a varus knee presented with the loss of the articular cartilage over the medial compartment. He underwent a high tibial osteotomy with the fixation of a Tomofix plate. Postoperative intraarticular injections of PBPC in combination

The medial femoral condyle underwent ideal subchondral drilling of the uncontained lesion (Fig 28). In the medial tibial plateau, ideal subchondral drilling was performed over the anterior half of the tibial plateau. Due to poor access, it was not possible to perform subchondral drilling over the posterior half of the tibial plateau. Therefore the "Inkwell"

with HA were given in accordance with the standard protocol.

Intraoperative view and (B) view at 18 months.

half.

29 and 32).

procedure was applied over the posterior half of the tibial plateau (Fig 29).

Fig. 28. The corresponding arthroscopic views over the medial femoral condyle. (A)

Fig. 29. (A) Arthroscopic view with black arrow showing ideal subchondral drilling over the

Fig 30 shows the radiological reappearance of the medial articulation at 7 months after surgery. MRI scan at 18 months confirmed the presence of repair cartilage over the anterior half of the medial compartment (Fig 31), confirmed on second-look arthroscopy (Fig 29). This is in contrast with the repair appearance of the posterior half of the tibial plateau (Figs

anterior half of the medial tibial plateau. Red arrow showing the multiple "inkwells" created in the posterior half of the medial tibial plateau. The blue line indicates the border separating the two distinct procedures. (B) Second-look arthroscopy at 18 months showing ideal chondrogenesis in the anterior half of the tibial plateau as compared to the posterior

Fig 30. A 53-year-old male underwent high tibial osteotomy: (A) Preoperative XR showing narrowing of medial compartment; and (B) Postoperative view at 7 months showing reappearance of the medial compartment.

Fig. 31. Preoperative (Pre-op) MRI (STIR) showing 'bone on bone' over the medial compartment of the right knee (red arrow). White arrow showing regenerated articular cartilage at 18 months over the anterior half of both the medial femoral condyle and medial tibial plateau.

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Fig. 33. Case 6 – Histological features showing hyaline cartilage regeneration from the

medial femoral condyle and medial tibial plateau biopsies.

Fig. 32. (A) Sagittal MRI (STIR) over the medial compartment. White arrow over the anterior half of the medial tibial plateau showing evidence of chondrogenesis. Red arrow over the posterior half of the medial tibial plateau whereby the "Inkwell" technique was applied showed minimal chondrogenesis. (B) Coronal MRI (STIR) over the posterior half of the medial tibial plateau. White arrow over the medial femoral condyle showing chondrogenesis. Red arrow over the medial tibial plateau showed minimal chondrogenesis.

Histology from the chondral core biopsy of the medial femoral condyle and anterior half of the medial tibial plateau confirmed the regeneration of hyaline cartilage (Fig 33).This case further supports the theory of ideal drilling with abrasion chondroplasty in uncontained lesions (Figs 26 and 28). With ideally placed drill holes and abrasion chondroplasty, there will be a larger volume of blood-clot scaffold for the injected PBPC and HA to form closely integrated individual tufts of cartilage. These closely seeded tufts arising from the subchondral bone will eventually coalesce to cover the bony defect. Chondrogenesis with maturation will result in increasing thickness of the regenerated cartilage covering the entire defect.

In the absence of subchondral drilling over the posterior half of the medial tibial plateau, the "Inkwell" procedure only produces minimal surface coverage as compared to the anterior half of the tibial plateau.

**Case 7**: A 45-year-old woman underwent right knee arthroscopic lateral patellar release and ideally placed subchondral drilling to the lateral patella facet and lateral trochlear (Fig 34). Beginning one week after surgery, 5 weekly intraarticular injections of HA were given to the operated knee. No PBPC was added to the HA during the intraarticular injections. Radiographs (Fig 35) show improvement of the lateral patellofemoral articulation. In the absence of PBPC in combination with HA, the repair process was only patchy in some areas and the regenerated tissue was found to be of fibrocartilage in nature (Fig 34 and 36).

Fig. 32. (A) Sagittal MRI (STIR) over the medial compartment. White arrow over the anterior half of the medial tibial plateau showing evidence of chondrogenesis. Red arrow over the posterior half of the medial tibial plateau whereby the "Inkwell" technique was applied showed minimal chondrogenesis. (B) Coronal MRI (STIR) over the posterior half of the medial tibial plateau. White arrow over the medial femoral condyle showing

Histology from the chondral core biopsy of the medial femoral condyle and anterior half of the medial tibial plateau confirmed the regeneration of hyaline cartilage (Fig 33).This case further supports the theory of ideal drilling with abrasion chondroplasty in uncontained lesions (Figs 26 and 28). With ideally placed drill holes and abrasion chondroplasty, there will be a larger volume of blood-clot scaffold for the injected PBPC and HA to form closely integrated individual tufts of cartilage. These closely seeded tufts arising from the subchondral bone will eventually coalesce to cover the bony defect. Chondrogenesis with maturation will result in increasing thickness of the regenerated cartilage covering the entire

In the absence of subchondral drilling over the posterior half of the medial tibial plateau, the "Inkwell" procedure only produces minimal surface coverage as compared to the anterior

**Case 7**: A 45-year-old woman underwent right knee arthroscopic lateral patellar release and ideally placed subchondral drilling to the lateral patella facet and lateral trochlear (Fig 34). Beginning one week after surgery, 5 weekly intraarticular injections of HA were given to the operated knee. No PBPC was added to the HA during the intraarticular injections. Radiographs (Fig 35) show improvement of the lateral patellofemoral articulation. In the absence of PBPC in combination with HA, the repair process was only patchy in some areas

and the regenerated tissue was found to be of fibrocartilage in nature (Fig 34 and 36).

chondrogenesis. Red arrow over the medial tibial plateau showed minimal

chondrogenesis.

defect.

half of the tibial plateau.

Fig. 33. Case 6 – Histological features showing hyaline cartilage regeneration from the medial femoral condyle and medial tibial plateau biopsies.

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Fig. 36. Case 7 - Histological features showing fibrocartilage repair from the lateral patella

The importance of adjuvant PBPC in combination with HA is well emphasised in this case. In the absence of PBPC, even though ideal subchondral drilling was performed, intraarticular injections of HA alone is ineffective in complete coverage of the bony drill

**Case 8**: A 49-year-old man underwent high tibial osteotomy with Tomofix plate fixation, lateral patellar release and ideal subchondral drilling into the tri-compartmental chondral defects. PBPC in combination with HA were injected intraarticularly into the operated knee 1 week after surgery for a total of five weeks. Postoperative radiographs at 19 months showed reappearance of the lateral patella articulation and improvement of the medial

Second-look arthroscopy with chondral core biopsy from the lateral trochlear (Fig 38), medial and lateral femoral condyles (Fig 39) showed evidence of hyaline cartilage regeneration (Fig 40). In contrast to case 7 which presented with only chondral defects over the lateral patellofemoral joint, case 8 showed satisfactory chondrogenesis with hyaline cartilage regeneration in all 3 compartments. With the addition of postoperative intraarticular injections of PBPC and HA following subchondral drilling, it is possible to address multiple chondral lesions in addition to the difficult to treat "Kissing" lesions.

facet and lateral trochlear biopsies.

compartment (Fig 37).

holes and initiate satisfactory articular cartilage repair.

Fig. 34. A 45-year-old woman with intraoperative (Intra-op) and second-look arthroscopy at 19 months. Despite ideal drilling but without postoperative intraarticular injections of PBPC + HA, the end result was only patchy coverage of the bony defects.

Fig. 35. (A) Preoperative (Pre-op) merchant view showing lateral patellar maltracking with absence of the lateral patellofemoral articulation. (B) XR at 18 months showed improvement of the lateral patellofemoral articulation.

Fig. 34. A 45-year-old woman with intraoperative (Intra-op) and second-look arthroscopy at 19 months. Despite ideal drilling but without postoperative intraarticular injections of PBPC

Fig. 35. (A) Preoperative (Pre-op) merchant view showing lateral patellar maltracking with absence of the lateral patellofemoral articulation. (B) XR at 18 months showed improvement

+ HA, the end result was only patchy coverage of the bony defects.

of the lateral patellofemoral articulation.

Fig. 36. Case 7 - Histological features showing fibrocartilage repair from the lateral patella facet and lateral trochlear biopsies.

The importance of adjuvant PBPC in combination with HA is well emphasised in this case. In the absence of PBPC, even though ideal subchondral drilling was performed, intraarticular injections of HA alone is ineffective in complete coverage of the bony drill holes and initiate satisfactory articular cartilage repair.

**Case 8**: A 49-year-old man underwent high tibial osteotomy with Tomofix plate fixation, lateral patellar release and ideal subchondral drilling into the tri-compartmental chondral defects. PBPC in combination with HA were injected intraarticularly into the operated knee 1 week after surgery for a total of five weeks. Postoperative radiographs at 19 months showed reappearance of the lateral patella articulation and improvement of the medial compartment (Fig 37).

Second-look arthroscopy with chondral core biopsy from the lateral trochlear (Fig 38), medial and lateral femoral condyles (Fig 39) showed evidence of hyaline cartilage regeneration (Fig 40). In contrast to case 7 which presented with only chondral defects over the lateral patellofemoral joint, case 8 showed satisfactory chondrogenesis with hyaline cartilage regeneration in all 3 compartments. With the addition of postoperative intraarticular injections of PBPC and HA following subchondral drilling, it is possible to address multiple chondral lesions in addition to the difficult to treat "Kissing" lesions.

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Fig. 39. Second-look at the medial and lateral femoral condyles showed satisfactory

**Intraoperative** 

Fig. 40. Case 8 - Histological features showing hyaline cartilage regeneration from the LT,

chondrogenesis.

LFC & MFC biopsies.

**Preoperative Postoperative 19 months**

Fig. 37. A 49-year-old man underwent high tibial osteotomy, lateral patellar release and tricompartmental chondral drilling.

Fig. 38. Second-look at 19 months showed satisfactory coverage of the bony defects by the regenerated tissue.

Fig. 37. A 49-year-old man underwent high tibial osteotomy, lateral patellar release and tri-

**Preoperative Postoperative 19 months**

Fig. 38. Second-look at 19 months showed satisfactory coverage of the bony defects by the

**Intraoperative** 

compartmental chondral drilling.

regenerated tissue.

**Intraoperative** 

Fig. 39. Second-look at the medial and lateral femoral condyles showed satisfactory chondrogenesis.

Fig. 40. Case 8 - Histological features showing hyaline cartilage regeneration from the LT, LFC & MFC biopsies.

Articular Cartilage Regeneration with Stem Cells 167

shorter intervals for our first 10 patients. Scans were performed on the first postoperative day as a baseline to document the chondral defect after debridement and subchondral drilling. Serial studies were then collected in the postoperative period (at 6, 12, 18, 24 months and beyond) to evaluate the filling of the defect by regenerated cartilage and

Fig. 41. Articular cartilage as depicted by sagittal PD image at the tibial plateau. Black arrow showing the surface of the tibial plateau articular cartilage and red arrow showing the "Black line" that separates the articular cartilage from the subchondral bone. This layer correlates with the tidemark / calcified cartilage / subchondral bone plate layers.

Fig. 42. A patient with her right knee in a high field extremity (1.5T) MRI (GE Medical

changes in the subchondral bone.

Systems).

#### **7.4.8 The importance of PBPC + HA as adjuvant therapy following ideal subchondral drilling**

Case 6 emphasizes on the importance of the improved technique of ideal drilling in an uncontained lesion. Cases 7 & 8 illustrates the importance of postoperative intraarticular injections of PBPC + HA.

Possible reasons as to why the microfracture technique has not been successful in achieving consistent coverage with hyaline cartilage can be explained by what is seen on second-look arthroscopy in cases 6, 7 and 8. Firstly, microfractures are usually placed 3 to 5 mm apart and do not penetrate much deeper than the calcified cartilage layer. Microfractures placed more superficially and further apart as compared to ideal subchondral drilling explains one of the possible reasons why the microfracture technique is inconsistent in producing satisfactory articular cartilage repair. Secondly, like the animal model in Fig 9, without postoperative adjunct therapy with PBPC + HA, the regenerated tissue will always be of inferior quality.
