What's new in limb lengthening and deformity correction

The Association of Tibia Femur Ratio and Degenerative Disease of the Spine, Hips, and Knees

BACKGROUND

When individuals with asymmetric lower extremities present for evaluation of limb-length inequality, correction can occur at the tibia, femur, or in both bones; however, there are limited data available to justify either technique. The aim of this study is to examine the normal ratio of tibia length/femur length (T/F), and to explore the relationship between T/F ratio and osteoarthritis of the spine, hips, and knees.

METHODS

Bone lengths of 1152 cadaveric femora and tibiae from the Hamann-Todd osteological collection were measured. Degenerative joint disease was graded in the hip, knee, and spine. Correlations between the ratio of T/F and osteoarthritis were evaluated with multiple regression analysis.

RESULTS

The average ratio of T/F was 0.80±0.03. There was a strong correlation between age and arthritis at all sites, with standardized β ranging from 0.44 to 0.57 (P<0.0005 for all). There was a significant correlation between increasing T/F and hip arthritis (standardized β=0.08, P=0.006), and knee arthritis (standardized β=0.08, P=0.008).

DISCUSSION

Increasing tibia length relative to femur length was found to be a significant predictor of ipsilateral hip and knee arthritis. Therefore, we recommend that when performing limb lengthening, surgical planning should lean toward recreating the normal ratio of 0.80. In circumstances where one bone is to be overlengthened relative to the other, bias should be toward overlengthening the femur. This same principle can be applied to limb-reduction surgery, where in certain circumstances, one may choose to preferentially shorten the tibia.

CLINICAL RELEVANCE

This is the first study to report long-term consequences of lower extremity segment disproportion.

Nutlin-3 treatment spares cisplatin-induced inhibition of bone healing while maintaining osteosarcoma toxicity

The majority of Osteosarcoma (OS) patients are treated with a combination of chemotherapy, resection, and limb salvage protocols. These protocols include distraction osteogenesis (DO), which is characterized by direct new bone formation. Cisplatin (CDP) is extensively used for OS chemotherapy and recent studies, using a mouse DO model, have demonstrated that CDP has profound negative effects on bone repair. Recent oncological therapeutic strategies are based on the use of standard cytotoxic drugs plus an assortment of biologic agents. Here we demonstrate that the previously reported CDP-associated inhibition of bone repair can be modulated by the administration of a small molecule p53 inducer (nutlin-3). The effects of nutlin-3 on CDP osteotoxicity were studied using both pre- and post-operative treatment models. In both cases the addition of nutlin-3, bracketing CDP exposure, demonstrated robust and significant bone sparing activity (p < 0.01-0.001). In addition the combination of nutlin-3 and CDP induced equivalent OS tumor killing in a xenograft model. Collectively, these results demonstrate that the induction of p53 peri-operatively protects bone healing from the toxic effects of CDP, while maintaining OS toxicity. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1716-1724, 2016.

What is the Utility Of a Limb Lengthening and Reconstruction Service in an Academic Department of Orthopaedic Surgery?

BACKGROUND

Limb lengthening and reconstruction surgery is a relatively new subspecialty of orthopaedic surgery in the United States. Despite increased awareness and practice of the specialty, it is rarely vested as a separate clinical service in an academic department of orthopaedic surgery. We have had experience growing such a dedicated service within an academic department of orthopaedic surgery over the past 9 years.

QUESTIONS/PURPOSES

We explored (1) the use of a limb deformity service (LDS) in an academic department of orthopaedic surgery by examining data on referral patterns, our clinical volume, and academic productivity; and (2) the surgical breadth of cases comprising the patients of the LDS in an academic department of orthopaedic surgery by examining data on caseload by anatomic sites, category, and surgical techniques/tools.

METHODS

We (SRR, ATF, EWB) retrospectively examined data on numbers of surgical cases and outpatient visits from the limb lengthening and complex reconstruction service at the Hospital for Special Surgery from 2005 to 2013 to evaluate growth. We studied 672 consecutive surgical cases performed by our service for a sample period of 1 year, assessing referral patterns within and outside our medical center, anatomic region, surgical category, and surgical technique/tool. Academic productivity was measured by review of our service's publications.

RESULTS

During the time period studied (2005-2013), outpatient and surgical volume significantly increased by 120% (1530 to 3372) and 105% (346 to 708), respectively, on our LDS. Surgical volume growth was similar to the overall growth of the department of orthopaedic surgery. Referrals were primarily from orthopaedic surgeons (56%) and self/Internet research (25%). Physician referrals were predominantly from our own medical center (83%). Referrals from within our institution came from a variety of clinical services. Forty-nine peer-reviewed articles and 23 book chapters were published by staff members of our service. Anatomic surgical sites, surgical categories, and technique/tools used on our LDS were diverse, yet procedures were specialized to the discipline of limb deformity.

CONCLUSIONS

There is a substantial role for an LDS within an academic department of orthopaedic surgery. With establishment of a dedicated service comes focus and resources that establish an environment for growth in volume, intramural and extramural referral, and purposeful research and education. The majority of referrals were from orthopaedic surgeons from our own medical center, suggesting needfulness. The LDS provides patients access to specialized surgery. The number of intramural referrals suggests that the specialty service helps retain patients within our academic orthopaedic department. Future research will try to determine if such a dedicated service leads to improved outcomes, efficiency, and value.

LEVEL OF EVIDENCE

Level IV, retrospective study.

Cisplatin inhibits bone healing during distraction osteogenesis

Osteosarcoma (OS) is the most common malignant bone tumor affecting children and adolescents. Many patients are treated with a combination of chemotherapy, resection, and limb salvage protocols. Surgical reconstructions after tumor resection include structural allografts, non-cemented endoprostheses, and distraction osteogenesis (DO), which require direct bone formation. Although cisplatin (CDP) is extensively used for OS chemotherapy, the effects on bone regeneration are not well studied. The effects of CDP on direct bone formation in DO were compared using two dosing regimens and both C57BL/6 (B6) and tumor necrosis factor receptor 1 knockout (TNFR1KO) mice, as CDP toxicity is associated with elevated TNF levels. Detailed evaluation of the five-dose CDP regimen (2 mg/kg/day), demonstrated significant decreases in new bone formation in the DO gaps of CDP treated versus vehicle treated mice (p < 0.001). Further, no significant inhibitory effects from the five-dose CDP regimen were observed in TNFR1KO mice. The two-dose regimen significantly inhibited new bone formation in B6 mice. These results demonstrate that CDP has profound short term negative effects on the process of bone repair in DO. These data provide the mechanistic basis for modeling peri-operative chemotherapy doses and schedules and may provide new opportunities to identify molecules that spare normal cells from the inhibitory effects of CDP.