Pinning the Contralateral Hip in SCFE
SCFE is the most common adolescent hip disorder, and roughly a third of unilateral cases threaten to become bilateral within two years. No professional body has settled whether to pin the healthy hip preemptively, so the decision falls to clinical judgment and the numbers behind it.
Takeaways
- Roughly a third of unilateral slips become bilateral, most within 18 months. In a Michigan cohort, 37% of 224 children with SCFE had a bilateral slip, and when the second hip slipped later rather than simultaneously, 88% did so within 18 months of the first. A separate series found a subsequent contralateral slip in 36% of 227 patients, at a mean of 6.5 months. (Loder, Aronson & Greenfield, J Bone Joint Surg Am 1993;75:1141-1147; Yildirim et al, J Bone Joint Surg Am 2008;90:485-492, PMID 18310697)
- Stability, not symptom duration, predicts osteonecrosis. When Loder reclassified acute slips by weight-bearing ability, avascular necrosis developed in 47% of unstable hips (unable to bear weight even with crutches) and in 0% of stable ones. A satisfactory result followed in 96% of stable hips versus 47% of unstable hips. (Loder et al, J Bone Joint Surg Am 1993;75:1134-1140, PMID 8354671)
- A few identifiable patients carry most of the contralateral risk. In the largest modern series (3,528 patients), 15.3% developed a contralateral slip, and independent risk factors included age under 12 in boys (OR 1.85), severe obesity (OR 1.81), and low vitamin D (OR 5.75). (Momtaz et al, J Bone Joint Surg Am 2024;106:517-524, PMID 38271486)
- A posterior sloping angle over 14° on the unaffected hip flags most future slips. Hips that went on to slip had a mean PSA of 17.2° versus 10.8° in hips that stayed unilateral (p<0.001). A 14° cutoff for prophylactic fixation would have prevented 83.3% of contralateral slips at the cost of pinning 21.1% of hips unnecessarily, a number needed to treat of 1.79. (Phillips et al, J Bone Joint Surg Am 2013;95:146-150, PMID 23324962)
- Prophylactic pinning is not risk-free. Across 99 children who had the asymptomatic hip pinned, the prophylactic side developed avascular necrosis in 2%, a periimplant fracture in 2%, and symptomatic hardware in 3%, though no patient subsequently slipped on the pinned side. (Sankar et al, Clin Orthop Relat Res 2013;471:2118-2123, PMID 23129473)
- Two decision analyses modeling the identical choice reached opposite answers. One favored observation of the contralateral hip (expected value 9.5 versus 9.2 for pinning), tipping toward pinning only once subsequent-slip probability exceeds 27%. A second analysis, using literature bilaterality rates reported as high as 80%, favored prophylactic pinning outright. (Kocher et al, J Bone Joint Surg Am 2004;86:2658-2665, PMID 15590850; Schultz et al, J Bone Joint Surg Am 2002, PMID 12177258)
- A head-to-head comparison found similar avascular necrosis whether the hip was pinned or watched. Of hips only observed, 19% later slipped and 2% overall developed AVN or chondrolysis. Of hips prophylactically pinned, 2% developed AVN and 3% needed reoperation, with similar rates of limp and leg-length difference between groups. (Haus et al, Orthop J Sports Med 2019)