Does Adding Femoral Lengthening at the Time of Rotation Hip Transposition After Periacetabular Tumor Resection Allow for Restoration of Limb Length and Function? Interim Results of a Modified Hip Transposition Procedure
Authors: Xu Hairong , Li Yuan , Zhang Qing , Hao Lin , Yu Feng , Niu Xiaohui 
Published: February 2021

Abstract

Background
Reconstruction after pelvic tumor resection of the acetabulum is challenging. Previous methods of hip transposition after acetabular resection have the advantages of reducing wound complications and infections of the allograft or metal endoprosthesis but were associated with substantial limb length discrepancy. We therefore developed a modification of this procedure, rotation hip transposition after femur lengthening, to address limb length, and we wished to evaluate its effectiveness in terms of complications and functional outcomes.

Questions/purposes
In this study, we asked: (1) What were the Musculoskeletal Tumor Society scores after this reconstruction method was used? (2) What complications occurred after this reconstruction method was used? (3) What proportion of patients achieved solid arthrodesis (as opposed to pseudarthrosis) with the sacrum and solid union of the femur? (4) What were the results with respect to limb length after a minimum follow-up of 2 years?

Methods
From 2011 to 2017, 83 patients with an aggressive benign or primary malignant tumor involving the acetabulum were treated in our institution. Of those, 23% (19 of 83) were treated with rotation hip transposition after femur lengthening and were considered for this retrospective study; 15 were available at a minimum follow-up of 2 years (median [range], 49 months [24 to 97 months]), and four died of lung metastases before 2 years. No patients were lost to follow-up before 2 years. During the period in question, the general indications for this approach were primary nonmetastatic malignant bone tumor or a locally aggressive benign bone tumor that could not be treated adequately with curettage. There were seven men and 12 women with a median age of 43 years. Nine patients underwent Zones I + II resection, eight patients had Zones I + II + III resection, and two received Zones II + III resection. After tumor resection, rotation hip transposition after femur lengthening reconstruction was performed, which included two steps. The first step was to lengthen the femur with the insertion of an allograft. Two methods were used to achieve limb lengthening: a “Z” osteotomy and a transverse osteotomy. The second step was to take the hip transposition and rotate the femoral head posteriorly 10° to 20°. The median (range) operative time was 510 minutes (330 to 925 minutes). The median intraoperative blood loss was 4000 mL (1800 to 7000 mL). We performed a chart review on the 15 available patients for clinical and radiographic assessment of functional outcomes and complications. Arthrodesis and leg length discrepancy were evaluated radiographically.

Results
The median (range) Musculoskeletal Tumor Society score was 21 points (17 to 30). Eleven of 19 patients developed procedure-related complications, including six patients with allograft nonunion, two with deep infection, two with delayed skin healing, and one with a hematoma. Two patients had minor additional surgical interventions without the removal of any implants. Local recurrences developed in four patients, and all four died of disease. All seven patients treated with a Z osteotomy had bone union. Among the eight patients with transverse osteotomy, bone union did not occur in six patients. After hip transposition, stable iliofemoral arthrodesis was achieved in seven patients. Pseudarthrosis developed in the remaining eight patients. The median (range) lower limb length discrepancy at the last follow-up visit or death was 8 mm (1 to 42 mm).

Conclusion
Although complex and challenging, rotation hip transposition after femur lengthening reconstruction with a Z osteotomy provides acceptable functional outcomes with complications that are within expectations for resection of pelvic tumors involving the acetabulum. Because of the magnitude and complexity of this technique, we believe it should be used primarily for patients with a favorable prognosis, both locally and systemically. This innovative procedure may be useful to other surgeons if larger numbers of patients and longer-term follow-up confirm our results.

Level of Evidence
Level IV, therapeutic study.