Effects of lower limb length discrepancy on spinopelvic compensation following total hip arthroplasty in patients with developmental dysplasia of the hip.

BACKGROUND: Limited research has examined the impact of lower limb length discrepancy (LLLD) alteration on spinopelvic compensation in individuals with developmental dysplasia of the hip (DDH). This study aimed to investigate the effects of LLLD on spinopelvic compensation following total hip arthroplasty (THA) and elucidate the complex biomechanical adaptations in the spinopelvic structures. METHODS: A retrospective review of DDH patients undergoing THA from January 2014 to December 2021 categorized individuals with Crowe type I and II into the low dislocation group (LDG, n = 94) and those with Crowe type III and IV into the high dislocation group (HDG, n = 43). Demographic data, as well as preoperative, postoperative, and last follow-up imaging data, including lower limb length (LLL), sacral obliquity (SO), iliac obliquity (IO), hip obliquity (HO), Cobb angle, apical vertebral translation (AVT), and coronal decompensation (CD), were collected for analysis. RESULTS: Patients in the LDG had a significantly higher surgical age and shorter disease duration (P<0.05). In LDG, patients exhibited substantial postoperative reductions in LLLD, SO, IO, and HO (P<0.05), while Cobb Angle, AVT, and CD showed no statistically significant changes (P>0.05). The variation in LLLD correlated significantly with the variations in SO, IO, and HO (P<0.05). Postoperative outcomes in the HDG demonstrated marked decreases in LLLD, SO, IO, HO, and CD (P<0.05), with no significant change in Cobb angle and AVT (P>0.05). The variation in LLLD correlated significantly with the variations in SO, IO, HO, and CD (P<0.05). CONCLUSIONS: THA effectively reduces LLLD in patients with DDH, and the variation in LLLD correlates meaningfully with the recovery of spinopelvic compensatory mechanisms.

Medium-term evaluation of leg lengthening by ISKD® intramedullary nail in 28 patients: Should we still use this lengthening system?

INTRODUCTION: Lower-limb lengthening presently uses intramedullary nailing. There are motorized systems and mechanical systems, each with their specific complications. The aim of the present study was to assess the efficacy of ISKD® mechanical nails (Orthofix Inc., Texas, USA) on 3D EOS® imaging, and also complications and functional impact. HYPOTHESIS: The study hypothesis was that nail lengthening is effective but should no longer use the ISKD® system, due to the high rate of specific complications. MATERIAL AND METHODS: A single-center retrospective study included 28 patients (14 female, 14 male) undergoing limb-lengthening by ISKD® nail between 2005 and 2018. Mean age was 29 years. Twenty-four procedures were femoral and 4 tibial. Lengthening and consolidation parameters and residual discrepancy were measured on 3D EOS® imaging. Complications and functional scores were collated. RESULTS: Twenty-eight ISKD® nails were implanted in 28 patients. Mean follow-up was 75 months. Planned lengthening was achieved in 78.5% of cases, for a mean lengthening of 34.5mm. Mean lengthening and consolidation indices were respectively 0.94mm/day and 105 days/cm. Length discrepancy showed significant correction, with improvement in functional scores (p<0.01). The overall complications rate was 67.9%, 76% of which were specific to the ISKD® nail. DISCUSSION: The present study confirmed that nail lengthening is an indication of choice in lower-limb length discrepancy, but that the ISKD® system should no longer be used, due to an excessive rate of specific complications. Complications are due to deficient control of lengthening rate, not found with new-generation motorized nails, which show much fewer complications. LEVEL OF EVIDENCE: IV, retrospective study without control group.