**5. Presence of low back pain**

Hip reconstruction surgery has the potential to restore hip mobility to normal levels and remove the secondary effects of limited hip motion on the lumbar spine. Improvement in low back pain after THA has been consistently reported. Parvizi et al. studied 170 patients with low back pain prior to undergoing THA [51]. Postoperatively, 66% (113) patients reported complete resolution of low back pain [51]. Of the 57 patients whose back pain did not resolve postoperatively, 38 had prior suspected or diagnosed spine disorders [51]. Chimenti et al. reported that 60.5% of patients who underwent THA had at least mild back pain preoperatively, and 58.4% of these patients experienced improvement in low back pain of at least 1 degree difference (e.g. moderate to mild) [52]. Notably, 80% of patients who indicated severe low back pain preoperatively showed some degree of pain improvement after THA [52]. Okuzu et al. reported that low back pain improved in 62.9% of patients after THA [53]. Persistent low back pain in the remaining 37.1% of patients after THA was shown to be associated with biomechanical abnormalities of the spine, such as sagittal spinal imbalance and high Cobb angle [53]. A study by Ran et al. examined changes in low back pain after THA in patients with lumbar degenerative disease, and observed a decreased on VAS for pain from 4.13 ± 1.37 preoperatively to 1.90 ± 1.44 postoperatively [54].

Patients with existing spinal pathologies present higher rates of complications after THA. Blizzard et al. conducted a review of the Medicare Standard Analytical Files from 2005 to 2012 [55]. The authors reported that patients with lumbosacral spondylosis, lumbar disc herniation, lumbar degenerative disc disease, and spondylolisthesis prior to THA had increased risk of post-operative complications such as prosthetic joint dislocation, periprosthetic fractures, periprosthetic infections, early revision THA, and wound complications [55].

Less evidence is available on hip preservation surgery and low back pain. Beck et al. reported that patients with a history of lumbosacral pathology (i.e. stenosis, fracture, prior surgery, and disc pathology) had significantly lower Hip Outcome Scores (activities of daily living subscale and sports subscale), modified Harris Hip Score, and visual analog scale pain two years after hip arthroscopy [56]. In contrast, in a cohort of 48 elite athletes with low back pain who underwent hip arthroscopy, Jiminez et al. reported that 79% did not report low back pain postoperatively at a mean follow-up of 53 months [57]. Endoscopic treatment for ischiofemoral impingement has also been associated with improvement in low back pain. Hatem et al. studied 31 patients with ischiofemoral impingement and low back pain who were treated with endoscopic partial lesser trochanter resection [58]. The authors reported a decrease in low back pain above the minimal clinically important difference in 2 of 3 patients after partial resection of the lesser trochanter [58]. Surgical correction of abnormal femoral torsion with derotation osteotomy has also been associated with improvement in low back pain. Hatem et al. reported that 14 patients with abnormal femoral torsion and LBP who underwent femoral derotation osteotomy demonstrated improved Oswestry disability index scores from 45% ± 16% (mean ± SD) before the PFDO to 22% ± 17% (mean ± SD) at mean follow-up of 24 months [37]. Nine (64.3%) of the 14 patients presented improvement in the Oswestry disability index above the minimal clinically important difference [37].
