How Does Thoracic Kyphosis Affect Patient Outcomes in Growing Rod Surgery?

Spine (Phila Pa 1976). 2011 Dec 28;

Authors: Schroerlucke SR, Akbarnia BA, Pawelek JB, Salari P, Mundis GM, Yazici M, Emans JB, Sponseller PD,

Abstract
Study Design. Retrospective review of a multi-center series.Objective. This study was conducted to specifically identify the complication rate of growing rod surgery in patients with normal (10-40?) versus abnormal thoracic kyphosis.Summary of Background Data. Surgical treatment options for progressive early onset scoliosis include spinal fusion versus growth-sparing techniques. The current most commonly employed growing rod technique involves short fusions at the foundation sites using either hooks or screws as anchors and placement of dual growing rods spanning the deformity. Although the coronal deformity in these patients has been studied extensively, the sagittal profile has received less attention as a possible factor in complication rates and patients outcomes.Methods. Out of 387 patients who underwent surgical placement of growing rods, 90 patients had complete clinical and radiographic data with two-year follow-up after initial surgery. Patients were categorized into three groups based on the magnitude of pre-operative thoracic kyphosis: <10 degrees (K- group), 10-40 degrees (N group) and >40 degrees (K+ group). Patient diagnosis, demographics, surgical information, radiographic measurements and complication types were tabulated and analyzed. A p value of <0.05 was considered significant for all statistical tests.Results. The K- group experienced 27 total complications including 15 general medical complications; the N group had 20 total and 4 general, and the K+ group had 55 total and 22 general complications. Patients in the K+ group were 3.1 times more likely to experience a complication than patients in the N group, which was statistically significant (p<0.05). When considering all types of complications, length of follow-up, T2-T5 proximal kyphosis, post-operative Cobb angle and rod diameter were identified as confounding variables. When the confounding variables were taken into consideration in the analysis, the odds ratios were no longer significant between the N and K+ groups. Patients in the K+ group and K- group were 2.95 and 2.89 times more likely to experience a general medical complication compared to those the N group, respectively (p>0.05). The rate of implant-related complications between the groups did not reach statistical significance, although the K+ group had the most implant complications (n = 34), including 25 rod breakages in 16 patients. Syndromic patients had 2.9 times the risk of having an overall complication when compared to the entire patient series (p<0.05). The number of patients who experienced multiple complications was higher in the K- and K+ groups than in the N group.Conclusion. Patients with thoracic hyper-kyphosis present even more of a challenge with respect to complications, specifically implant-related complications. Our study shows that growing rod surgery in patients with kyphosis >40? have significantly more general and implant complications than patients with normal thoracic kyphosis. Implant complications were more common in hyper-kyphotic (>40?) patients and increased linearly with increasing kyphosis. The most common implant complication was rod breakage. Patients with hyper-kyphotic thoracic spines, particularly syndromic patients, must be monitored closely and parents should be counseled regarding the likelihood of future adverse events.

PMID: 22210014 [PubMed – as supplied by publisher]

The Use of a Transition Rod May Prevent Proximal Junctional Kyphosis in the Thoracic Spine Following Scoliosis Surgery: A Finite Element Analysis.

Spine (Phila Pa 1976). 2011 Dec 28;

Authors: Cahill PJ, Wang W, Asghar J, Booker R, Betz RR, Ramsey C, Baran G

Abstract
Study Design. Finite element analysisObjective. Via finite element analysis: 1) to demonstrate the abnormal forces present at the top of a scoliosis construct, 2) to demonstrate the importance of an intact interspinous and supraspinous ligament (ISL/SSL) complex, and 3) to evaluate a transition rod (a rod that has a short taper to a smaller diameter at one end) as an implant solution to diminish these pathomechanics, regardless of the integrity of the ISL/SSL complex.Summary of Background Data. The pathophysiology of increased nucleus pressure and increased angular displacement may contribute to proximal junctional kyphosis. Furthermore, high implant stress can be demonstrated at the upper end of the construct, possibly leading to risk of implant failure.Methods. A finite element model was constructed to simulate a thoracic spinal fusion. The model was altered to remove the ISL/SSL complex at the level above the construct. Lastly, the model was altered again by extending the construct one level superior with a transition rod. The angular displacement, the maximum pressure in the nucleus, and stress within the implant were extracted from computational results under two conditions: load control and displacement control. The testing was performed with both titanium and stainless steel implants.Results. Pressure in the nucleus and angular displacement are all increased when the ISL/SSL complex is removed immediately above the instrumented levels, while the screw pull-out force and maximum stress within the screw is decreased. The nucleus pressure increases by over 50%. The angular displacement increases 19-26%. This absence of the ISL/SSL complex simulates the clinical scenario that occurs when these structures are iatrogenically detached. Abnormal mechanics can be restored to normal level by extending the construct rostral one level with a transition rod. Furthermore, the elevated nucleus pressure and angular displacement noted even when the ISL/SSL complex is intact can be avoided with the use of a transition rod. Under the same bending moment (3 Nm), the nucleus pressure at the level immediately cephalad is up to 23% lower than the pressure in a standard construct. The angular displacement is 18-19% less than the standard construct. The maximum implant stress is also decreased by as much as 60%.Conclusions. Finite element modeling suggests that the pathomechanics at the proximal end of a scoliosis construct may be diminished by preserving the ISL/SSL complex and possibly completely eliminated with the use of rods with a diameter transition at the most proximal level.

PMID: 22210013 [PubMed – as supplied by publisher]

Proximal junctional kyphosis in adult reconstructive spine surgery results from incomplete restoration of the lumbar lordosis relative to the magnitude of the thoracic kyphosis.

Iowa Orthop J. 2011;31:199-206

Authors: Mendoza-Lattes S, Ries Z, Gao Y, Weinstein SL

Abstract
BACKGROUND: PROXIMAL JUNCTIONAL KYPHOSIS (PJK) IS DEFINED AS: 1) Proximal junction sagittal Cobb angle >?10°, and 2) Proximal junction sagittal Cobb angle of at least 10° greater than the pre-operative measurement PJK is a common complication which develops in 39% of adults following surgery for spinal deformity. The pathogenesis, risk factors and prevention of this complication are unclear.
METHODS: Of 54 consecutive adults treated with spinal deformity surgery (age?59.3±10.1 years), 19 of 54 (35%) developed PJK. The average follow-up was 26.8months (range 12 – 42). Radiographic parameters were measured at the pre-operative, early postoperative (4-6 weeks), and final follow-up visits. Sagittal alignment was measured by the ratio between the C7-plumbline and the sacral-femoral distance. Binary logistic regression model with predictor variables included: Age, BMI, C7-plumbline, and whether lumbar lordosis, thoracic kyphosis and sacral slope were present
RESULTS: Patients who developed PJK and those without PJK presented with comparable age, BMI, pelvic incidence and sagittal imbalance before surgery. They also presented with comparable sacral slope and lumbar lordosis. The average magnitude of thoracic kyphosis was significantly larger than the lumbar lordosis in the proximal junctional kyphosis group, both at baseline and in the early postoperative period, as represented by [(-lumbar )lordosis – (thoracic kyphosis)]; no- PJK versus PJK; 6.6°±23.2° versus -6.6°±14.2°; p?0.012. This was not effectively addressed with surgery in the PJK group [(-LL-TK): 6.2°±13.1° vs. -5.2°±9.6°; p?0.004]. This group also presented with signs of pelvic retroversion with a sacral slope of 29.3°±8.2° pre-operatively that was unchanged after surgery (30.4°±8.5° postoperatively). Logistic regression determined that the magnitude of thoracic kyphosis and sagittal balance (C7-plumbline) was the most important predictor of proximal junctional kyphosis.
CONCLUSIONS: Proximal junctional kyphosis developed in those patients where the thoracic kyphosis remained greater in magnitude relative to the lumbar lordosis, and where the sagittal balance seemed corrected, but part of thise correction was secondary to pelvic retroversion.
LEVEL OF EVIDENCE: Prognostic case-control study – Level III.

PMID: 22096442 [PubMed – in process]

Anterior-posterior surgery versus posterior closing wedge osteotomy in posttraumatic kyphosis with neurologic compromised osteoporotic fracture.

Spine (Phila Pa 1976). 2003 Sep 15;28(18):2170-5

Authors: Suk SI, Kim JH, Lee SM, Chung ER, Lee JH

Retrospective study.

PMID: 14501932 [PubMed – indexed for MEDLINE]

Treatment of severe postburn kyphosis with combined plastic surgery and milwaukee bracing.

Spine (Phila Pa 1976). 2002 Jun 1;27(11):E288-90

Authors: Winter RB, Pilney FT

A case is reported in which severe postburn kyphosis is treated with combined plastic surgery and Milwaukee bracing.

PMID: 12045532 [PubMed – indexed for MEDLINE]

Three-stage surgery in the management of severe rigid angular kyphosis.

Eur Spine J. 2002 Apr;11(2):107-14

Authors: Sar C, Eralp L

There are conflicting data regarding the management of rigid kyphosis. None of the currently known techniques can completely correct severe kyphosis without resulting in residual deformity. Seven patients with local kyphosis exceeding 60 degrees were operated on to achieve complete correction of the deformity. The surgery consisted of total spondylectomy of the deformed vertebra and simultaneous application of compression-distraction forces to this area. The operation included three stages: The initial stage includes resection of posterior spinal elements and temporary fixation. In the second stage, an anterior corpectomy is performed to conclude the resection, and simultaneous antero-posterior correction is obtained. The final stage includes another posterior procedure to achieve a precise correction and to correct any compensatory curves. All patients were operated on using this technique in a single session. The mean preoperative and postoperative kyphosis angles were 76.1 degrees (range, 65 degrees -92 degrees) and 6 degrees (range, 0 degrees -13 degrees), respectively. Complete bony fusion was achieved after a mean follow-up period of 38 months (range, 26-52 months) without any neurological sequelae or significant loss of correction.

PMID: 11956915 [PubMed – indexed for MEDLINE]

Does instrumented anterior scoliosis surgery lead to kyphosis, pseudarthrosis, or inadequate correction in adults?

Spine (Phila Pa 1976). 2002 Mar 1;27(5):529-34

Authors: Smith JA, Deviren V, Berven S, Bradford DS

Retrospective review of cases in which a single solid rod was used for the anterior correction of thoracolumbar and lumbar idiopathic scoliosis in adults.

PMID: 11880839 [PubMed – indexed for MEDLINE]

Circumferential cervical surgery for spondylostenosis with kyphosis in two patients with athetoid cerebral palsy.

Surg Neurol. 1999 Oct;52(4):339-44

Authors: Epstein NE

Patients with athetoid cerebral palsy may develop severe degenerative changes in the cervical spine decades earlier than their normal counterparts due to abnormal cervical motion.

PMID: 10555838 [PubMed – indexed for MEDLINE]

[Multiplan correction of a 3D deformity : Options and relevance of optimizing the thoracic kyphosis in reconstructive scoliosis surgery].

Orthopade. 2011 Aug;40(8):672-81

Authors: Wiedenhöfer B, Fürstenberg CH, Schröder K, Akbar M

There is presently still no consensus on how to operatively treat adolescent idiopathic scoliosis (AIS), i.e. a clearly reduced thoracic kyphosis. For a long time the primary focus was mostly on correcting the coronal plane while neglecting the sagittal profile. Based on the current literature and own retrospective data a comprehensive review will be given on the optimal correction of the spine and how to avoid secondary complications. Different operative standard procedures are demonstrated with special attention to the sagittal balance and the special parameters sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), sagittal slope (SSL) and pelvic incidence (PI).

PMID: 21751031 [PubMed – in process]

Neurological complications of anterior spinal surgery for kyphosis with normal somatosensory evoked potentials (SEPs).

J Neurol Neurosurg Psychiatry. 1999 May;66(5):662-4

Authors: Pelosi L, Jardine A, Webb JK

We report a case of neurological complications of anterior release for correction of kyphosis. After the operation, the patient had pyramidal weakness and decreased pain sensation below T5, whereas light touch, proprioception and vibration sensation were intact. Clinical and neurophysiological findings in this patient suggested a partial lesion of the spinal cord probably due to ischaemia in the territory of the anterior spinal artery. Intraoperative and postoperative tibial nerve SEPs remained normal, which stresses the need for recording from the motor pathways.

PMID: 10209183 [PubMed – indexed for MEDLINE]

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